P23FB: Cylinder 10 Injector B Air-Fuel Ratio Imbalance

P23FB marks cylinder 10, the highest cylinder number of a V10. Among dual-injection engines, the Huracán's 5.2 litre unit is the documented case; it adds multi-point injection to direct injection. In its firing order cylinder 10 follows directly after cylinder 5. On a ten-cylinder engine an injector B deviation in cylinder 10 shows up mainly in the bank that includes cylinders 6 to 10, which is why a bank code (P219B) or a misfire code (P0310) may be the only entry. CARB requires imbalance detection for such cars too, and since 2019 to 2021 also tracking of how frequently the check runs to completion in everyday use. No manufacturer documents P23FB publicly. P21A5 and the circuit code P21D8 are the companion codes.

High severity. Can I keep driving?Avoid driving if the light is flashing or the engine is shaking: unburned gasoline can damage the catalytic converter.

Cylinder 10 is numbered according to the manufacturer: check your engine's manual before working on it.

Symptoms

Check engine light on
Bank 2 or misfire code stored alongside
Mostly no noticeable change

Most likely causes

Port injector of cylinder 10 dirty or worn
Injector seal leaking air at cylinder 10
Heat-damaged wiring to injector B of cylinder 10 (check P21D8)

What to check, in order

Start with the simplest. You can tick off each step.

See whether the light is flashing: if so, reduce engine load and avoid driving
Inspect the spark plugs, coils, and connectors
Swap the coil with another cylinder and see if the misfire moves with it
Check the injector and look for air leaks
Run a compression test if everything above checks out

Good to know

It affects emissions.

What each character of P23FB means

P: Powertrain: engine and transmission
2: Generic code: same on every make
3: Ignition and misfires
FB: Specific fault in that system

Frequently asked questions

Can I keep driving with code P23FB?

Avoid driving if the light is flashing or the engine is shaking: unburned gasoline can damage the catalytic converter.

What causes code P23FB?

The most common causes are: port injector of cylinder 10 dirty or worn; injector seal leaking air at cylinder 10; heat-damaged wiring to injector B of cylinder 10 (check P21D8).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.